One of the crucial factors affecting the performance of a compressor is its mechanical efficiency. For example, the reciprocating piston-cylinder compressor exhibits good mechanical efficiency, but its reciprocating action results in significant vibration and noise problems. To negate such problems, rotary type compressors have been developed and have since gained much popularity due to their compact nature and good vibration Characteristics. However, as their parts in sliding contact generally possess high relative velocities, frictional losses are predominant and have thus limited the efficiency and reliability of the machines. For instance, in Rotary Sliding Vane compressors, the rotor and vane tips rub against the cylinder interior at high velocities, resulting in enormous frictional losses. Similarly, in Rolling-Piston compressors, the rolling piston rubbing against the eccentric and the cylinder interior also result in significant losses. It is therefore believed that if the relative velocities of the rubbing components in rotary compressors can be effectively reduced, their overall performance and reliability can be improved substantially.